Study On The Rapid Detection Method Of Endosulfan Residues In Agricultural Products

Two competitive immunoassays, a laboratory assay based on microwell plates and a field test based on the use of polystyrene tubes, have been developed for the detection of endosulfan in agricultural products. And the efficiencies were evaluated systemically. The limit of detection for microwell plate was 0.8 ± 0.1 μg/kg and for tube was 1.6 ± 0.2 μg/kg. The specificity of the polyclonal antibody was good and each parameter was stable.Three different extraction methods were employed and 82.6%-112% recoveries of spiked samples were obtained. Although the recovery values obtained from the method by hand-shaking for 5 min were somewhat lower than those obtained from other two methods, this method was also reasonable efficient, extracting over 80% of the residue in every sample. Moreover, by reason that this extraction method did not require the instruments for extraction, it was the simplest extraction method of the tested methods and reproducible enough to be used for extraction for on-site residue analysis.The matrix effect was studied in ELISA. Methanol extracts of some agricultural product samples could be analyzed directly by immunoassay after dilution in 0.5% fish skin gelatin-phosphate buffered saline. In contrast, extracts of green tea caused significant interference in the assay, and a number of simple clean-up methods were ineffective in removing interference. However, use of the coagulating reagent — Polyvinyl Pyrrolidone removes matrix effect effectively.Before the GC analysis, three clean-up methods were employed. The result indicated that the SPE method was the best choice and it could clean up samples effectively.For the validation of the ELISA tests, samples were analyzed by ELISA and GC. The relationship between data obtained using tube assay and microwell assay was good and also the immunoassay assay data correlated well with data obtained from GC analysis. The developed ELISA methods are the suitable methods for the rapid quantitative and reliable detection of endosulfan in agricultural products.